In the proposed work an analysis will be made of changes in proliferation kinetics and associated molecular controls, that enable DNA synthesis and proliferative activity to persist in gastrointestinal cells of expanding neoplasms. Measurements of kinetic parameters will be made in isolated non-hereditary neoplasms of man, and those induced in rodents by a chemical carcinogen 1,2-dimethylhydrazine. Simultaneous measurements will be continued to define the pattern of activity of enzymes involved in DNA synthesis in the cells of the expanding neoplasms. In studies of cell proliferation kinetics, measurements of cell cycle parameters are being made as well as estimates of growth rate of neoplasms, birth rate of cells and growth fraction. A new measurement, growth coefficient, is being used to quantitate cell retention in the phase 2 proliferative kinetic lesion previously described. The findings in isolated non-hereditary neoplasms of man are being correlated with those observed in rodents after the chemical carcinogen, to assess with increased accuracy factors governing the ability of cells to retain their proliferative activity in expanding neoplasms.